Abstract

Introduction

Interleukin (IL)-21 is a cytokine that controls the functional activity of effector
T helper cells and the differentiation of Th17 cells, and promotes B-cell differentiation.
To test whether IL-21 participates in the pathogenesis of primary Sjögren's syndrome
(SS), serum IL-21 level was measured and IL-21 expression in the labial salivary glands
(LSG) was examined.

Results

Primary SS patients had significantly higher serum IL-21 levels than controls, and
these increments correlated positively with levels of IgG, IgG1. Serum IgG1 levels
correlated with anti-Ro antibody titers. Immunohistochemical analyses showed that
lymphocytic foci and the periductal area of the LSGs from SS patients expressed high
levels of IL-21 and lower levels of IL-21R, whereas the control LSGs showed minimal
expression of both antigens. The more the lymphocyte infiltrated, IL-21expression
in LSGs showed a tendency to increase. Confocal microscopic analyses revealed that
IL-21 expressing infiltrating lymphocytes in the LSGs of SS patients also expressed
CXCR5.

Conclusions

Primary SS is associated with high serum IL-21 levels that correlate positively with
serum IgG, especially IgG1, levels. The expression of IL-21 is increased as more lymphocytes
infiltrated in LSGs. These observations suggest that IL-21 may play an important role
in primary SS pathogenesis.